mainloop
          This procedure sets up a top-level event loop.   Events
          are  processed  until  there  are  no more active event
          sources, at which time the process exits.  It  is  used
          to  build  event oriented programs using the TclX shell
          in a style similar to that used with wish.  If the glo-
          bal  variable  tcl_interactive  exists  and  has a true
          value an interactive  command  handler  is  started  as
          well.   If the command handler is terminated by an EOF,
          the process will be exited.

          This commands is not useful in wishx, as  it  automati-
          cally enters an event loop after processing a script.

          This procedure is provided by Extended Tcl.